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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2011 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except<a name="line.4"></a>
<span class="sourceLineNo">005</span> * in compliance with the License. You may obtain a copy of the License at<a name="line.5"></a>
<span class="sourceLineNo">006</span> *<a name="line.6"></a>
<span class="sourceLineNo">007</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.7"></a>
<span class="sourceLineNo">008</span> *<a name="line.8"></a>
<span class="sourceLineNo">009</span> * Unless required by applicable law or agreed to in writing, software distributed under the License<a name="line.9"></a>
<span class="sourceLineNo">010</span> * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express<a name="line.10"></a>
<span class="sourceLineNo">011</span> * or implied. See the License for the specific language governing permissions and limitations under<a name="line.11"></a>
<span class="sourceLineNo">012</span> * the License.<a name="line.12"></a>
<span class="sourceLineNo">013</span> */<a name="line.13"></a>
<span class="sourceLineNo">014</span><a name="line.14"></a>
<span class="sourceLineNo">015</span>package com.google.common.collect;<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>import com.google.common.annotations.Beta;<a name="line.17"></a>
<span class="sourceLineNo">018</span>import com.google.common.base.Preconditions;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.util.ArrayDeque;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.util.Collection;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.util.Deque;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.util.PriorityQueue;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import java.util.Queue;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import java.util.concurrent.ArrayBlockingQueue;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import java.util.concurrent.BlockingQueue;<a name="line.26"></a>
<span class="sourceLineNo">027</span>import java.util.concurrent.ConcurrentLinkedQueue;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.util.concurrent.LinkedBlockingDeque;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.concurrent.LinkedBlockingQueue;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.util.concurrent.PriorityBlockingQueue;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.util.concurrent.SynchronousQueue;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.util.concurrent.TimeUnit;<a name="line.32"></a>
<span class="sourceLineNo">033</span><a name="line.33"></a>
<span class="sourceLineNo">034</span>/**<a name="line.34"></a>
<span class="sourceLineNo">035</span> * Static utility methods pertaining to {@link Queue} and {@link Deque} instances.<a name="line.35"></a>
<span class="sourceLineNo">036</span> * Also see this class's counterparts {@link Lists}, {@link Sets}, and {@link Maps}.<a name="line.36"></a>
<span class="sourceLineNo">037</span> *<a name="line.37"></a>
<span class="sourceLineNo">038</span> * @author Kurt Alfred Kluever<a name="line.38"></a>
<span class="sourceLineNo">039</span> * @since 11.0<a name="line.39"></a>
<span class="sourceLineNo">040</span> */<a name="line.40"></a>
<span class="sourceLineNo">041</span>public final class Queues {<a name="line.41"></a>
<span class="sourceLineNo">042</span>  private Queues() {}<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>  // ArrayBlockingQueue<a name="line.44"></a>
<span class="sourceLineNo">045</span><a name="line.45"></a>
<span class="sourceLineNo">046</span>  /**<a name="line.46"></a>
<span class="sourceLineNo">047</span>   * Creates an empty {@code ArrayBlockingQueue} instance.<a name="line.47"></a>
<span class="sourceLineNo">048</span>   *<a name="line.48"></a>
<span class="sourceLineNo">049</span>   * @return a new, empty {@code ArrayBlockingQueue}<a name="line.49"></a>
<span class="sourceLineNo">050</span>   */<a name="line.50"></a>
<span class="sourceLineNo">051</span>  public static &lt;E&gt; ArrayBlockingQueue&lt;E&gt; newArrayBlockingQueue(int capacity) {<a name="line.51"></a>
<span class="sourceLineNo">052</span>    return new ArrayBlockingQueue&lt;E&gt;(capacity);<a name="line.52"></a>
<span class="sourceLineNo">053</span>  }<a name="line.53"></a>
<span class="sourceLineNo">054</span><a name="line.54"></a>
<span class="sourceLineNo">055</span>  // ArrayDeque<a name="line.55"></a>
<span class="sourceLineNo">056</span><a name="line.56"></a>
<span class="sourceLineNo">057</span>  /**<a name="line.57"></a>
<span class="sourceLineNo">058</span>   * Creates an empty {@code ArrayDeque} instance.<a name="line.58"></a>
<span class="sourceLineNo">059</span>   *<a name="line.59"></a>
<span class="sourceLineNo">060</span>   * @return a new, empty {@code ArrayDeque}<a name="line.60"></a>
<span class="sourceLineNo">061</span>   * @since 12.0<a name="line.61"></a>
<span class="sourceLineNo">062</span>   */<a name="line.62"></a>
<span class="sourceLineNo">063</span>  public static &lt;E&gt; ArrayDeque&lt;E&gt; newArrayDeque() {<a name="line.63"></a>
<span class="sourceLineNo">064</span>    return new ArrayDeque&lt;E&gt;();<a name="line.64"></a>
<span class="sourceLineNo">065</span>  }<a name="line.65"></a>
<span class="sourceLineNo">066</span><a name="line.66"></a>
<span class="sourceLineNo">067</span>  /**<a name="line.67"></a>
<span class="sourceLineNo">068</span>   * Creates an {@code ArrayDeque} instance containing the given elements.<a name="line.68"></a>
<span class="sourceLineNo">069</span>   *<a name="line.69"></a>
<span class="sourceLineNo">070</span>   * @param elements the elements that the queue should contain, in order<a name="line.70"></a>
<span class="sourceLineNo">071</span>   * @return a new {@code ArrayDeque} containing those elements<a name="line.71"></a>
<span class="sourceLineNo">072</span>   * @since 12.0<a name="line.72"></a>
<span class="sourceLineNo">073</span>   */<a name="line.73"></a>
<span class="sourceLineNo">074</span>  public static &lt;E&gt; ArrayDeque&lt;E&gt; newArrayDeque(Iterable&lt;? extends E&gt; elements) {<a name="line.74"></a>
<span class="sourceLineNo">075</span>    if (elements instanceof Collection) {<a name="line.75"></a>
<span class="sourceLineNo">076</span>      return new ArrayDeque&lt;E&gt;(Collections2.cast(elements));<a name="line.76"></a>
<span class="sourceLineNo">077</span>    }<a name="line.77"></a>
<span class="sourceLineNo">078</span>    ArrayDeque&lt;E&gt; deque = new ArrayDeque&lt;E&gt;();<a name="line.78"></a>
<span class="sourceLineNo">079</span>    Iterables.addAll(deque, elements);<a name="line.79"></a>
<span class="sourceLineNo">080</span>    return deque;<a name="line.80"></a>
<span class="sourceLineNo">081</span>  }<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span>  // ConcurrentLinkedQueue<a name="line.83"></a>
<span class="sourceLineNo">084</span><a name="line.84"></a>
<span class="sourceLineNo">085</span>  /**<a name="line.85"></a>
<span class="sourceLineNo">086</span>   * Creates an empty {@code ConcurrentLinkedQueue} instance.<a name="line.86"></a>
<span class="sourceLineNo">087</span>   *<a name="line.87"></a>
<span class="sourceLineNo">088</span>   * @return a new, empty {@code ConcurrentLinkedQueue}<a name="line.88"></a>
<span class="sourceLineNo">089</span>   */<a name="line.89"></a>
<span class="sourceLineNo">090</span>  public static &lt;E&gt; ConcurrentLinkedQueue&lt;E&gt; newConcurrentLinkedQueue() {<a name="line.90"></a>
<span class="sourceLineNo">091</span>    return new ConcurrentLinkedQueue&lt;E&gt;();<a name="line.91"></a>
<span class="sourceLineNo">092</span>  }<a name="line.92"></a>
<span class="sourceLineNo">093</span><a name="line.93"></a>
<span class="sourceLineNo">094</span>  /**<a name="line.94"></a>
<span class="sourceLineNo">095</span>   * Creates an {@code ConcurrentLinkedQueue} instance containing the given elements.<a name="line.95"></a>
<span class="sourceLineNo">096</span>   *<a name="line.96"></a>
<span class="sourceLineNo">097</span>   * @param elements the elements that the queue should contain, in order<a name="line.97"></a>
<span class="sourceLineNo">098</span>   * @return a new {@code ConcurrentLinkedQueue} containing those elements<a name="line.98"></a>
<span class="sourceLineNo">099</span>   */<a name="line.99"></a>
<span class="sourceLineNo">100</span>  public static &lt;E&gt; ConcurrentLinkedQueue&lt;E&gt; newConcurrentLinkedQueue(<a name="line.100"></a>
<span class="sourceLineNo">101</span>      Iterable&lt;? extends E&gt; elements) {<a name="line.101"></a>
<span class="sourceLineNo">102</span>    if (elements instanceof Collection) {<a name="line.102"></a>
<span class="sourceLineNo">103</span>      return new ConcurrentLinkedQueue&lt;E&gt;(Collections2.cast(elements));<a name="line.103"></a>
<span class="sourceLineNo">104</span>    }<a name="line.104"></a>
<span class="sourceLineNo">105</span>    ConcurrentLinkedQueue&lt;E&gt; queue = new ConcurrentLinkedQueue&lt;E&gt;();<a name="line.105"></a>
<span class="sourceLineNo">106</span>    Iterables.addAll(queue, elements);<a name="line.106"></a>
<span class="sourceLineNo">107</span>    return queue;<a name="line.107"></a>
<span class="sourceLineNo">108</span>  }<a name="line.108"></a>
<span class="sourceLineNo">109</span><a name="line.109"></a>
<span class="sourceLineNo">110</span>  // LinkedBlockingDeque<a name="line.110"></a>
<span class="sourceLineNo">111</span><a name="line.111"></a>
<span class="sourceLineNo">112</span>  /**<a name="line.112"></a>
<span class="sourceLineNo">113</span>   * Creates an empty {@code LinkedBlockingDeque} instance.<a name="line.113"></a>
<span class="sourceLineNo">114</span>   *<a name="line.114"></a>
<span class="sourceLineNo">115</span>   * @return a new, empty {@code LinkedBlockingDeque}<a name="line.115"></a>
<span class="sourceLineNo">116</span>   * @since 12.0<a name="line.116"></a>
<span class="sourceLineNo">117</span>   */<a name="line.117"></a>
<span class="sourceLineNo">118</span>  public static &lt;E&gt; LinkedBlockingDeque&lt;E&gt; newLinkedBlockingDeque() {<a name="line.118"></a>
<span class="sourceLineNo">119</span>    return new LinkedBlockingDeque&lt;E&gt;();<a name="line.119"></a>
<span class="sourceLineNo">120</span>  }<a name="line.120"></a>
<span class="sourceLineNo">121</span><a name="line.121"></a>
<span class="sourceLineNo">122</span>  /**<a name="line.122"></a>
<span class="sourceLineNo">123</span>   * Creates a {@code LinkedBlockingDeque} with the given (fixed) capacity.<a name="line.123"></a>
<span class="sourceLineNo">124</span>   *<a name="line.124"></a>
<span class="sourceLineNo">125</span>   * @param capacity the capacity of this deque<a name="line.125"></a>
<span class="sourceLineNo">126</span>   * @return a new, empty {@code LinkedBlockingDeque}<a name="line.126"></a>
<span class="sourceLineNo">127</span>   * @throws IllegalArgumentException if {@code capacity} is less than 1<a name="line.127"></a>
<span class="sourceLineNo">128</span>   * @since 12.0<a name="line.128"></a>
<span class="sourceLineNo">129</span>   */<a name="line.129"></a>
<span class="sourceLineNo">130</span>  public static &lt;E&gt; LinkedBlockingDeque&lt;E&gt; newLinkedBlockingDeque(int capacity) {<a name="line.130"></a>
<span class="sourceLineNo">131</span>    return new LinkedBlockingDeque&lt;E&gt;(capacity);<a name="line.131"></a>
<span class="sourceLineNo">132</span>  }<a name="line.132"></a>
<span class="sourceLineNo">133</span><a name="line.133"></a>
<span class="sourceLineNo">134</span>  /**<a name="line.134"></a>
<span class="sourceLineNo">135</span>   * Creates an {@code LinkedBlockingDeque} instance containing the given elements.<a name="line.135"></a>
<span class="sourceLineNo">136</span>   *<a name="line.136"></a>
<span class="sourceLineNo">137</span>   * @param elements the elements that the queue should contain, in order<a name="line.137"></a>
<span class="sourceLineNo">138</span>   * @return a new {@code LinkedBlockingDeque} containing those elements<a name="line.138"></a>
<span class="sourceLineNo">139</span>   * @since 12.0<a name="line.139"></a>
<span class="sourceLineNo">140</span>   */<a name="line.140"></a>
<span class="sourceLineNo">141</span>  public static &lt;E&gt; LinkedBlockingDeque&lt;E&gt; newLinkedBlockingDeque(Iterable&lt;? extends E&gt; elements) {<a name="line.141"></a>
<span class="sourceLineNo">142</span>    if (elements instanceof Collection) {<a name="line.142"></a>
<span class="sourceLineNo">143</span>      return new LinkedBlockingDeque&lt;E&gt;(Collections2.cast(elements));<a name="line.143"></a>
<span class="sourceLineNo">144</span>    }<a name="line.144"></a>
<span class="sourceLineNo">145</span>    LinkedBlockingDeque&lt;E&gt; deque = new LinkedBlockingDeque&lt;E&gt;();<a name="line.145"></a>
<span class="sourceLineNo">146</span>    Iterables.addAll(deque, elements);<a name="line.146"></a>
<span class="sourceLineNo">147</span>    return deque;<a name="line.147"></a>
<span class="sourceLineNo">148</span>  }<a name="line.148"></a>
<span class="sourceLineNo">149</span><a name="line.149"></a>
<span class="sourceLineNo">150</span>  // LinkedBlockingQueue<a name="line.150"></a>
<span class="sourceLineNo">151</span><a name="line.151"></a>
<span class="sourceLineNo">152</span>  /**<a name="line.152"></a>
<span class="sourceLineNo">153</span>   * Creates an empty {@code LinkedBlockingQueue} instance.<a name="line.153"></a>
<span class="sourceLineNo">154</span>   *<a name="line.154"></a>
<span class="sourceLineNo">155</span>   * @return a new, empty {@code LinkedBlockingQueue}<a name="line.155"></a>
<span class="sourceLineNo">156</span>   */<a name="line.156"></a>
<span class="sourceLineNo">157</span>  public static &lt;E&gt; LinkedBlockingQueue&lt;E&gt; newLinkedBlockingQueue() {<a name="line.157"></a>
<span class="sourceLineNo">158</span>    return new LinkedBlockingQueue&lt;E&gt;();<a name="line.158"></a>
<span class="sourceLineNo">159</span>  }<a name="line.159"></a>
<span class="sourceLineNo">160</span><a name="line.160"></a>
<span class="sourceLineNo">161</span>  /**<a name="line.161"></a>
<span class="sourceLineNo">162</span>   * Creates a {@code LinkedBlockingQueue} with the given (fixed) capacity.<a name="line.162"></a>
<span class="sourceLineNo">163</span>   *<a name="line.163"></a>
<span class="sourceLineNo">164</span>   * @param capacity the capacity of this queue<a name="line.164"></a>
<span class="sourceLineNo">165</span>   * @return a new, empty {@code LinkedBlockingQueue}<a name="line.165"></a>
<span class="sourceLineNo">166</span>   * @throws IllegalArgumentException if {@code capacity} is less than 1<a name="line.166"></a>
<span class="sourceLineNo">167</span>   */<a name="line.167"></a>
<span class="sourceLineNo">168</span>  public static &lt;E&gt; LinkedBlockingQueue&lt;E&gt; newLinkedBlockingQueue(int capacity) {<a name="line.168"></a>
<span class="sourceLineNo">169</span>    return new LinkedBlockingQueue&lt;E&gt;(capacity);<a name="line.169"></a>
<span class="sourceLineNo">170</span>  }<a name="line.170"></a>
<span class="sourceLineNo">171</span><a name="line.171"></a>
<span class="sourceLineNo">172</span>  /**<a name="line.172"></a>
<span class="sourceLineNo">173</span>   * Creates an {@code LinkedBlockingQueue} instance containing the given elements.<a name="line.173"></a>
<span class="sourceLineNo">174</span>   *<a name="line.174"></a>
<span class="sourceLineNo">175</span>   * @param elements the elements that the queue should contain, in order<a name="line.175"></a>
<span class="sourceLineNo">176</span>   * @return a new {@code LinkedBlockingQueue} containing those elements<a name="line.176"></a>
<span class="sourceLineNo">177</span>   */<a name="line.177"></a>
<span class="sourceLineNo">178</span>  public static &lt;E&gt; LinkedBlockingQueue&lt;E&gt; newLinkedBlockingQueue(Iterable&lt;? extends E&gt; elements) {<a name="line.178"></a>
<span class="sourceLineNo">179</span>    if (elements instanceof Collection) {<a name="line.179"></a>
<span class="sourceLineNo">180</span>      return new LinkedBlockingQueue&lt;E&gt;(Collections2.cast(elements));<a name="line.180"></a>
<span class="sourceLineNo">181</span>    }<a name="line.181"></a>
<span class="sourceLineNo">182</span>    LinkedBlockingQueue&lt;E&gt; queue = new LinkedBlockingQueue&lt;E&gt;();<a name="line.182"></a>
<span class="sourceLineNo">183</span>    Iterables.addAll(queue, elements);<a name="line.183"></a>
<span class="sourceLineNo">184</span>    return queue;<a name="line.184"></a>
<span class="sourceLineNo">185</span>  }<a name="line.185"></a>
<span class="sourceLineNo">186</span><a name="line.186"></a>
<span class="sourceLineNo">187</span>  // LinkedList: see {@link com.google.common.collect.Lists}<a name="line.187"></a>
<span class="sourceLineNo">188</span><a name="line.188"></a>
<span class="sourceLineNo">189</span>  // PriorityBlockingQueue<a name="line.189"></a>
<span class="sourceLineNo">190</span><a name="line.190"></a>
<span class="sourceLineNo">191</span>  /**<a name="line.191"></a>
<span class="sourceLineNo">192</span>   * Creates an empty {@code PriorityBlockingQueue} instance.<a name="line.192"></a>
<span class="sourceLineNo">193</span>   *<a name="line.193"></a>
<span class="sourceLineNo">194</span>   * @return a new, empty {@code PriorityBlockingQueue}<a name="line.194"></a>
<span class="sourceLineNo">195</span>   */<a name="line.195"></a>
<span class="sourceLineNo">196</span>  public static &lt;E&gt; PriorityBlockingQueue&lt;E&gt; newPriorityBlockingQueue() {<a name="line.196"></a>
<span class="sourceLineNo">197</span>    return new PriorityBlockingQueue&lt;E&gt;();<a name="line.197"></a>
<span class="sourceLineNo">198</span>  }<a name="line.198"></a>
<span class="sourceLineNo">199</span><a name="line.199"></a>
<span class="sourceLineNo">200</span>  /**<a name="line.200"></a>
<span class="sourceLineNo">201</span>   * Creates an {@code PriorityBlockingQueue} instance containing the given elements.<a name="line.201"></a>
<span class="sourceLineNo">202</span>   *<a name="line.202"></a>
<span class="sourceLineNo">203</span>   * @param elements the elements that the queue should contain, in order<a name="line.203"></a>
<span class="sourceLineNo">204</span>   * @return a new {@code PriorityBlockingQueue} containing those elements<a name="line.204"></a>
<span class="sourceLineNo">205</span>   */<a name="line.205"></a>
<span class="sourceLineNo">206</span>  public static &lt;E&gt; PriorityBlockingQueue&lt;E&gt; newPriorityBlockingQueue(<a name="line.206"></a>
<span class="sourceLineNo">207</span>      Iterable&lt;? extends E&gt; elements) {<a name="line.207"></a>
<span class="sourceLineNo">208</span>    if (elements instanceof Collection) {<a name="line.208"></a>
<span class="sourceLineNo">209</span>      return new PriorityBlockingQueue&lt;E&gt;(Collections2.cast(elements));<a name="line.209"></a>
<span class="sourceLineNo">210</span>    }<a name="line.210"></a>
<span class="sourceLineNo">211</span>    PriorityBlockingQueue&lt;E&gt; queue = new PriorityBlockingQueue&lt;E&gt;();<a name="line.211"></a>
<span class="sourceLineNo">212</span>    Iterables.addAll(queue, elements);<a name="line.212"></a>
<span class="sourceLineNo">213</span>    return queue;<a name="line.213"></a>
<span class="sourceLineNo">214</span>  }<a name="line.214"></a>
<span class="sourceLineNo">215</span><a name="line.215"></a>
<span class="sourceLineNo">216</span>  // PriorityQueue<a name="line.216"></a>
<span class="sourceLineNo">217</span><a name="line.217"></a>
<span class="sourceLineNo">218</span>  /**<a name="line.218"></a>
<span class="sourceLineNo">219</span>   * Creates an empty {@code PriorityQueue} instance.<a name="line.219"></a>
<span class="sourceLineNo">220</span>   *<a name="line.220"></a>
<span class="sourceLineNo">221</span>   * @return a new, empty {@code PriorityQueue}<a name="line.221"></a>
<span class="sourceLineNo">222</span>   */<a name="line.222"></a>
<span class="sourceLineNo">223</span>  public static &lt;E&gt; PriorityQueue&lt;E&gt; newPriorityQueue() {<a name="line.223"></a>
<span class="sourceLineNo">224</span>    return new PriorityQueue&lt;E&gt;();<a name="line.224"></a>
<span class="sourceLineNo">225</span>  }<a name="line.225"></a>
<span class="sourceLineNo">226</span><a name="line.226"></a>
<span class="sourceLineNo">227</span>  /**<a name="line.227"></a>
<span class="sourceLineNo">228</span>   * Creates an {@code PriorityQueue} instance containing the given elements.<a name="line.228"></a>
<span class="sourceLineNo">229</span>   *<a name="line.229"></a>
<span class="sourceLineNo">230</span>   * @param elements the elements that the queue should contain, in order<a name="line.230"></a>
<span class="sourceLineNo">231</span>   * @return a new {@code PriorityQueue} containing those elements<a name="line.231"></a>
<span class="sourceLineNo">232</span>   */<a name="line.232"></a>
<span class="sourceLineNo">233</span>  public static &lt;E&gt; PriorityQueue&lt;E&gt; newPriorityQueue(Iterable&lt;? extends E&gt; elements) {<a name="line.233"></a>
<span class="sourceLineNo">234</span>    if (elements instanceof Collection) {<a name="line.234"></a>
<span class="sourceLineNo">235</span>      return new PriorityQueue&lt;E&gt;(Collections2.cast(elements));<a name="line.235"></a>
<span class="sourceLineNo">236</span>    }<a name="line.236"></a>
<span class="sourceLineNo">237</span>    PriorityQueue&lt;E&gt; queue = new PriorityQueue&lt;E&gt;();<a name="line.237"></a>
<span class="sourceLineNo">238</span>    Iterables.addAll(queue, elements);<a name="line.238"></a>
<span class="sourceLineNo">239</span>    return queue;<a name="line.239"></a>
<span class="sourceLineNo">240</span>  }<a name="line.240"></a>
<span class="sourceLineNo">241</span><a name="line.241"></a>
<span class="sourceLineNo">242</span>  // SynchronousQueue<a name="line.242"></a>
<span class="sourceLineNo">243</span><a name="line.243"></a>
<span class="sourceLineNo">244</span>  /**<a name="line.244"></a>
<span class="sourceLineNo">245</span>   * Creates an empty {@code SynchronousQueue} instance.<a name="line.245"></a>
<span class="sourceLineNo">246</span>   *<a name="line.246"></a>
<span class="sourceLineNo">247</span>   * @return a new, empty {@code SynchronousQueue}<a name="line.247"></a>
<span class="sourceLineNo">248</span>   */<a name="line.248"></a>
<span class="sourceLineNo">249</span>  public static &lt;E&gt; SynchronousQueue&lt;E&gt; newSynchronousQueue() {<a name="line.249"></a>
<span class="sourceLineNo">250</span>    return new SynchronousQueue&lt;E&gt;();<a name="line.250"></a>
<span class="sourceLineNo">251</span>  }<a name="line.251"></a>
<span class="sourceLineNo">252</span>  <a name="line.252"></a>
<span class="sourceLineNo">253</span>  /**<a name="line.253"></a>
<span class="sourceLineNo">254</span>   * Drains the queue as {@link BlockingQueue#drainTo(Collection, int)}, but if the requested <a name="line.254"></a>
<span class="sourceLineNo">255</span>   * {@code numElements} elements are not available, it will wait for them up to the specified<a name="line.255"></a>
<span class="sourceLineNo">256</span>   * timeout.<a name="line.256"></a>
<span class="sourceLineNo">257</span>   * <a name="line.257"></a>
<span class="sourceLineNo">258</span>   * @param q the blocking queue to be drained<a name="line.258"></a>
<span class="sourceLineNo">259</span>   * @param buffer where to add the transferred elements<a name="line.259"></a>
<span class="sourceLineNo">260</span>   * @param numElements the number of elements to be waited for<a name="line.260"></a>
<span class="sourceLineNo">261</span>   * @param timeout how long to wait before giving up, in units of {@code unit}<a name="line.261"></a>
<span class="sourceLineNo">262</span>   * @param unit a {@code TimeUnit} determining how to interpret the timeout parameter<a name="line.262"></a>
<span class="sourceLineNo">263</span>   * @return the number of elements transferred<a name="line.263"></a>
<span class="sourceLineNo">264</span>   * @throws InterruptedException if interrupted while waiting<a name="line.264"></a>
<span class="sourceLineNo">265</span>   */<a name="line.265"></a>
<span class="sourceLineNo">266</span>  @Beta<a name="line.266"></a>
<span class="sourceLineNo">267</span>  public static &lt;E&gt; int drain(BlockingQueue&lt;E&gt; q, Collection&lt;? super E&gt; buffer, int numElements,<a name="line.267"></a>
<span class="sourceLineNo">268</span>      long timeout, TimeUnit unit) throws InterruptedException {<a name="line.268"></a>
<span class="sourceLineNo">269</span>    Preconditions.checkNotNull(buffer);<a name="line.269"></a>
<span class="sourceLineNo">270</span>    /*<a name="line.270"></a>
<span class="sourceLineNo">271</span>     * This code performs one System.nanoTime() more than necessary, and in return, the time to<a name="line.271"></a>
<span class="sourceLineNo">272</span>     * execute Queue#drainTo is not added *on top* of waiting for the timeout (which could make<a name="line.272"></a>
<span class="sourceLineNo">273</span>     * the timeout arbitrarily inaccurate, given a queue that is slow to drain).<a name="line.273"></a>
<span class="sourceLineNo">274</span>     */<a name="line.274"></a>
<span class="sourceLineNo">275</span>    long deadline = System.nanoTime() + unit.toNanos(timeout);<a name="line.275"></a>
<span class="sourceLineNo">276</span>    int added = 0;<a name="line.276"></a>
<span class="sourceLineNo">277</span>    while (added &lt; numElements) {<a name="line.277"></a>
<span class="sourceLineNo">278</span>      // we could rely solely on #poll, but #drainTo might be more efficient when there are multiple<a name="line.278"></a>
<span class="sourceLineNo">279</span>      // elements already available (e.g. LinkedBlockingQueue#drainTo locks only once)<a name="line.279"></a>
<span class="sourceLineNo">280</span>      added += q.drainTo(buffer, numElements - added);<a name="line.280"></a>
<span class="sourceLineNo">281</span>      if (added &lt; numElements) { // not enough elements immediately available; will have to poll<a name="line.281"></a>
<span class="sourceLineNo">282</span>        E e = q.poll(deadline - System.nanoTime(), TimeUnit.NANOSECONDS);<a name="line.282"></a>
<span class="sourceLineNo">283</span>        if (e == null) {<a name="line.283"></a>
<span class="sourceLineNo">284</span>          break; // we already waited enough, and there are no more elements in sight<a name="line.284"></a>
<span class="sourceLineNo">285</span>        }<a name="line.285"></a>
<span class="sourceLineNo">286</span>        buffer.add(e);<a name="line.286"></a>
<span class="sourceLineNo">287</span>        added++;<a name="line.287"></a>
<span class="sourceLineNo">288</span>      }<a name="line.288"></a>
<span class="sourceLineNo">289</span>    }<a name="line.289"></a>
<span class="sourceLineNo">290</span>    return added;<a name="line.290"></a>
<span class="sourceLineNo">291</span>  }<a name="line.291"></a>
<span class="sourceLineNo">292</span>  <a name="line.292"></a>
<span class="sourceLineNo">293</span>  /**<a name="line.293"></a>
<span class="sourceLineNo">294</span>   * Drains the queue as {@linkplain #drain(BlockingQueue, Collection, int, long, TimeUnit)}, <a name="line.294"></a>
<span class="sourceLineNo">295</span>   * but with a different behavior in case it is interrupted while waiting. In that case, the <a name="line.295"></a>
<span class="sourceLineNo">296</span>   * operation will continue as usual, and in the end the thread's interruption status will be set <a name="line.296"></a>
<span class="sourceLineNo">297</span>   * (no {@code InterruptedException} is thrown). <a name="line.297"></a>
<span class="sourceLineNo">298</span>   * <a name="line.298"></a>
<span class="sourceLineNo">299</span>   * @param q the blocking queue to be drained<a name="line.299"></a>
<span class="sourceLineNo">300</span>   * @param buffer where to add the transferred elements<a name="line.300"></a>
<span class="sourceLineNo">301</span>   * @param numElements the number of elements to be waited for<a name="line.301"></a>
<span class="sourceLineNo">302</span>   * @param timeout how long to wait before giving up, in units of {@code unit}<a name="line.302"></a>
<span class="sourceLineNo">303</span>   * @param unit a {@code TimeUnit} determining how to interpret the timeout parameter<a name="line.303"></a>
<span class="sourceLineNo">304</span>   * @return the number of elements transferred<a name="line.304"></a>
<span class="sourceLineNo">305</span>   */<a name="line.305"></a>
<span class="sourceLineNo">306</span>  @Beta<a name="line.306"></a>
<span class="sourceLineNo">307</span>  public static &lt;E&gt; int drainUninterruptibly(BlockingQueue&lt;E&gt; q, Collection&lt;? super E&gt; buffer, <a name="line.307"></a>
<span class="sourceLineNo">308</span>      int numElements, long timeout, TimeUnit unit) {<a name="line.308"></a>
<span class="sourceLineNo">309</span>    Preconditions.checkNotNull(buffer);<a name="line.309"></a>
<span class="sourceLineNo">310</span>    long deadline = System.nanoTime() + unit.toNanos(timeout);<a name="line.310"></a>
<span class="sourceLineNo">311</span>    int added = 0;<a name="line.311"></a>
<span class="sourceLineNo">312</span>    boolean interrupted = false;<a name="line.312"></a>
<span class="sourceLineNo">313</span>    try {<a name="line.313"></a>
<span class="sourceLineNo">314</span>      while (added &lt; numElements) {<a name="line.314"></a>
<span class="sourceLineNo">315</span>        // we could rely solely on #poll, but #drainTo might be more efficient when there are <a name="line.315"></a>
<span class="sourceLineNo">316</span>        // multiple elements already available (e.g. LinkedBlockingQueue#drainTo locks only once)<a name="line.316"></a>
<span class="sourceLineNo">317</span>        added += q.drainTo(buffer, numElements - added);<a name="line.317"></a>
<span class="sourceLineNo">318</span>        if (added &lt; numElements) { // not enough elements immediately available; will have to poll<a name="line.318"></a>
<span class="sourceLineNo">319</span>          E e; // written exactly once, by a successful (uninterrupted) invocation of #poll<a name="line.319"></a>
<span class="sourceLineNo">320</span>          while (true) {<a name="line.320"></a>
<span class="sourceLineNo">321</span>            try {<a name="line.321"></a>
<span class="sourceLineNo">322</span>              e = q.poll(deadline - System.nanoTime(), TimeUnit.NANOSECONDS);<a name="line.322"></a>
<span class="sourceLineNo">323</span>              break;<a name="line.323"></a>
<span class="sourceLineNo">324</span>            } catch (InterruptedException ex) {<a name="line.324"></a>
<span class="sourceLineNo">325</span>              interrupted = true; // note interruption and retry<a name="line.325"></a>
<span class="sourceLineNo">326</span>            }<a name="line.326"></a>
<span class="sourceLineNo">327</span>          }<a name="line.327"></a>
<span class="sourceLineNo">328</span>          if (e == null) {<a name="line.328"></a>
<span class="sourceLineNo">329</span>            break; // we already waited enough, and there are no more elements in sight<a name="line.329"></a>
<span class="sourceLineNo">330</span>          }<a name="line.330"></a>
<span class="sourceLineNo">331</span>          buffer.add(e);<a name="line.331"></a>
<span class="sourceLineNo">332</span>          added++;<a name="line.332"></a>
<span class="sourceLineNo">333</span>        }<a name="line.333"></a>
<span class="sourceLineNo">334</span>      }<a name="line.334"></a>
<span class="sourceLineNo">335</span>    } finally {<a name="line.335"></a>
<span class="sourceLineNo">336</span>      if (interrupted) {<a name="line.336"></a>
<span class="sourceLineNo">337</span>        Thread.currentThread().interrupt();<a name="line.337"></a>
<span class="sourceLineNo">338</span>      }<a name="line.338"></a>
<span class="sourceLineNo">339</span>    }<a name="line.339"></a>
<span class="sourceLineNo">340</span>    return added;<a name="line.340"></a>
<span class="sourceLineNo">341</span>  }<a name="line.341"></a>
<span class="sourceLineNo">342</span><a name="line.342"></a>
<span class="sourceLineNo">343</span>  /**<a name="line.343"></a>
<span class="sourceLineNo">344</span>   * Returns a synchronized (thread-safe) queue backed by the specified queue. In order to<a name="line.344"></a>
<span class="sourceLineNo">345</span>   * guarantee serial access, it is critical that &lt;b&gt;all&lt;/b&gt; access to the backing queue is<a name="line.345"></a>
<span class="sourceLineNo">346</span>   * accomplished through the returned queue.<a name="line.346"></a>
<span class="sourceLineNo">347</span>   *<a name="line.347"></a>
<span class="sourceLineNo">348</span>   * &lt;p&gt;It is imperative that the user manually synchronize on the returned queue when accessing<a name="line.348"></a>
<span class="sourceLineNo">349</span>   * the queue's iterator: &lt;pre&gt;   {@code<a name="line.349"></a>
<span class="sourceLineNo">350</span>   *<a name="line.350"></a>
<span class="sourceLineNo">351</span>   *   Queue&lt;E&gt; queue = Queues.synchronizedQueue(MinMaxPriorityQueue&lt;E&gt;.create());<a name="line.351"></a>
<span class="sourceLineNo">352</span>   *   ...<a name="line.352"></a>
<span class="sourceLineNo">353</span>   *   queue.add(element);  // Needn't be in synchronized block<a name="line.353"></a>
<span class="sourceLineNo">354</span>   *   ...<a name="line.354"></a>
<span class="sourceLineNo">355</span>   *   synchronized (queue) {  // Must synchronize on queue!<a name="line.355"></a>
<span class="sourceLineNo">356</span>   *     Iterator&lt;E&gt; i = queue.iterator(); // Must be in synchronized block<a name="line.356"></a>
<span class="sourceLineNo">357</span>   *     while (i.hasNext()) {<a name="line.357"></a>
<span class="sourceLineNo">358</span>   *       foo(i.next());<a name="line.358"></a>
<span class="sourceLineNo">359</span>   *     }<a name="line.359"></a>
<span class="sourceLineNo">360</span>   *   }}&lt;/pre&gt;<a name="line.360"></a>
<span class="sourceLineNo">361</span>   *<a name="line.361"></a>
<span class="sourceLineNo">362</span>   * Failure to follow this advice may result in non-deterministic behavior.<a name="line.362"></a>
<span class="sourceLineNo">363</span>   *<a name="line.363"></a>
<span class="sourceLineNo">364</span>   * &lt;p&gt;The returned queue will be serializable if the specified queue is serializable.<a name="line.364"></a>
<span class="sourceLineNo">365</span>   *<a name="line.365"></a>
<span class="sourceLineNo">366</span>   * @param queue the queue to be wrapped in a synchronized view<a name="line.366"></a>
<span class="sourceLineNo">367</span>   * @return a synchronized view of the specified queue<a name="line.367"></a>
<span class="sourceLineNo">368</span>   * @since 14.0<a name="line.368"></a>
<span class="sourceLineNo">369</span>   */<a name="line.369"></a>
<span class="sourceLineNo">370</span>  @Beta<a name="line.370"></a>
<span class="sourceLineNo">371</span>  public static &lt;E&gt; Queue&lt;E&gt; synchronizedQueue(Queue&lt;E&gt; queue) {<a name="line.371"></a>
<span class="sourceLineNo">372</span>    return Synchronized.queue(queue, null);<a name="line.372"></a>
<span class="sourceLineNo">373</span>  }<a name="line.373"></a>
<span class="sourceLineNo">374</span>}<a name="line.374"></a>




























































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